First and foremost, streamers choose what or who to promote and that's their choice because we all know it's about the money for them.
Secondly, streamers can't be solely responsible for fueling addiction because the industry expects users to be of a certain age to make informed decisions as an adult!!!.
To me it is quite unfair how some people dare to judge steamers based on what they advertise or promote, for example, some weeks ago there were streamers who were promoting a game called "Concord" which was pretty much a bad game and one of the biggest flops in the game industry, and yet they were paid to promote and say it was a pretty good addicting game for everyone to enjoy.
Being a streamer or an influencer is not easy, it means one is self-employed and one needs to carefully decide which sponsors who is going to accept and which ones one will turn away. Those streamers we are rather new and with a small number of viewers are in more pressure to accept being sponsored by casinos and gambling platforms, they are the ones which offer the most money and they ones which pay more attention to the community of streamers in the making.
I have seen 1xbet being sponsoring small YouTube channels which did not have anything to do with gambling, for example.
Whether one is an adult and has access to internet is quite irrelevant to the issue as it stands for now, though. It is very easy to cheat one's age in this modern era, even though KYC seems to be everywhere, it has not been applied yet in streaming and video services like YT.